So I have a javascript file named "flash_portfolio_300x250.js" but inside my index file its referencing "flash_portfolio_300x250.js?1465837255984". so I have a client trying to upload this to google display network and they keep getting an error message and are anything but pleased at the moment. I didn't know they were using google display network so I had no idea what the issue was. Once i found out that they were using it I ran my files through their validator and found the issue

<script src="flash_portfolio_300x250.js?1465837255984"></script>

I don't have a file named this. the name of the file is this

<script src="flash_portfolio_300x250.js"></script>

once i got rid of those numbers at the end of the file name the validator came back as good.

To clarify something marjantrajkovski said, it's ok for you to do test in browser, and have those numbers appear, that will solve caching issues while you're developing. But, for the one you send to the client, go to File/Publish, and publish that way. Then it does not add those numbers.